1. Technical Field
This disclosure relates to insulated structural panels used in building construction. In particular, the present disclosure relates to insulated structural roof panels including a combination of structural metal components and rigid foam insulation.
2. Related Art
Traditional building construction typically uses wood or metal stud framing with fiberglass insulation enclosed with a drywall interior wall and a wood or stucco exterior wall. These types of conventional structures do not have efficient thermal insulating properties, use many types of non-recyclable materials, and are labor-intensive to build.
More recently, prefabricated panels made of two sheets of plywood or oriented strand board (OSB) with rigid foam insulation between the boards have been used to construct walls, floors, and/or roofs of buildings. These prefabricated panels, called “structural insulated panels” (SIP) may be fabricated at a manufacturing plant and shipped to a jobsite for rapid erection of a building. The SIP's are stronger and have better insulation properties than a framed lumber building. However, SIP's also have inefficient thermal insulation properties and can be susceptible to insect infestation, wood decay from excessive trapped moisture, mold, and/or mildew.
U.S. Patent Application No. 20060117689, filed on Nov. 18, 2005, and names Ronnie and Yelena Onken as inventors (herein the Onken patent application) describes an insulated structural panel formed with a rigid foam core, a plurality of vertical hat channels on either face of the rigid foam core, and horizontal top and bottom L-channels on either face of the rigid foam core. The plurality of vertical hat channels on opposing faces of the rigid foam core is attached together so as to compress the rigid foam core, thus adding structural strength to the insulated structural panel. However, the ties used to attach the hat channels in the Onken patent application create undesirable thermal bridging between the opposing faces of the rigid foam core. This undesirable thermal bridging reduces the thermal insulation efficiency of the Onken panel. Further, the vertical hat channel described in the Onken patent application is expensive to manufacture and uses an excessive amount of material in the fabrication of the hat channel.
Typical existing SIP's that utilize a rigid foam core and hat channel studs often require a mechanical fastener. Typical existing SIP's that utilize rigid foam core and hat channel studs typically have a void between an opposing face of the studs to allow for the mechanical fastener between the parallel hat channels. This void makes it more difficult to attach interior and exterior sheathing. The mechanical fastener provides a thermal bridge and diminishes the insulating value of the panel making the structure less energy efficient. Typical SIP's that utilize a rigid foam core and hat channel studs have notches that are cut out of the foam. The overall insulating value of the panel is less than a panel without notches cut out. Typical SIP's that utilize a rigid foam core and hat channel studs are glued to adjacent panels, but the connection is still a hinge point with no structural value for bending. Consequently, the panel spans between the top and bottom plates or foundation. Typical SIP's that utilize a rigid foam core and hat channel studs typically have a glued butt connection at the corners. This butt connection is of minimal structural value and does not allow for ready attachment of interior sheathing. Typical SIP's that utilize a rigid foam core and hat channel studs require a stiffened lip to take advantage of the bending strength of the section, due to flange buckling effects seen in sections of this type.
U.S. Pat. No. 5,921,046 describes a building assembly for efficiently and economically constructing walls, roofs, and floors using a prefabricated building panel made essentially of a plastic foam core with a thin coating of plastic resin or acrylic and portland cement applied on each side for structural rigidity, the building panel having a standardized semicircular recess disposed about its perimeter for receiving pre-sized, cylindrical connectors also made of foam with a coating, and half-round connectors that connect the panel to a slab, and that also fit in the horizontal perimeter recesses of each panel.
Thus, a structural insulated roof panel with a rigid foam core is needed.